Many attempts have been made to produce an ideal flow pattern for the charge of air and fuel within the combustion chamber of an internal combustion engine. Considerations that must be taken into effect include, but are not limited to, providing for adequate power generation, minimizing the NOx entrained in the engine exhaust, and minimizing the amount of soot particulate also entrained in the engine exhaust. These last two considerations should be accomplished without hurting the fuel economy of the engine and without adversely affecting the power output of the engine.
It is known that changes in any one of a variety of engine design/operating variables, such as engine compression ratio, combustion chamber shape, fuel injection spray pattern, and other variables can have an affect on both emissions and power generated.
The amount of soot that is expelled with the engine's exhaust is unsightly and generates public pressure to clean up diesel engines. Further, the amount of soot that is entrained in the engine's lubrication oil can have a deleterious effect on engine reliability. Soot is very abrasive and can cause high engine wear.
There is additionally a great deal of pressure to reduce the NOx emissions from the engine. Ever increasing regulatory demands mandate reduced levels of NOx. Typically, a combustion chamber design that is effective at reducing NOx levels has been found to increase the levels of soot and vice-versa. Additionally, doing either of the aforementioned typically reduces engine torque and power outputs.
There are numerous examples of combustion chambers formed in the crown of a piston. Notwithstanding all these prior art designs, there remains a need for reduction both in NOx and entrained soot while at the same time maintaining or enhancing engine torque and power outputs without adversely affecting the fuel economy of the engine.